What was a primary objective of the US foreign policy during the 1930s?
The basic objective of any government's foreign policy is to further the interests of the nation it serves. With that said, foreign policy is geared to making sure the nation is secure militarily by forming military and trade agreements that produce wealth and help pay for the military. Foreign policy leaders negotiate with friendly and unfriendly world powers to ensure the aforementioned objectives.
Containment of communism. From the end of WW2 to 1989 when the Berlin Wall fell the foreign policy of the United States was to contain communism. The result was keeping troops in Europe so if the Russians decided to invade they could be stopped, the United States entering Southeast Asia and the Vietnam war, and the Cuban boycott for 60 years are just a few examples of the policy of containment.
American foreign policy during the Cold War had two primary objectives. The first was to deter explicit Communist aggression (primarily from the Soviet Union) towards the United States and its allies through the use of nuclear arms and other conventional weapons. The second was to counter Communist expansion into other world-nations through indirect means, although direct means (as in Korean and Vietnam) were sometimes utilized, as well.
There is no "a" foreign policy. Every national political group - especially but not exclusively states - pursues it's own foreign policy. There has been countless stances of foreign policy before, during, and since World War One. You need to be more specific for a less general answer - say, inquiring about the foreign policy stance of the United States, or Russia, or some other nation.
It would depend which aspects of U.S. foreign policy you are interested in following. The White House website does list some of the president's current achievements in foreign policy. But for an objective view of what he believes and what he is trying to achieve, I recommend such magazines as Time, Foreign Policy, and The Week; newspapers like the Washington Post, Wall Street Journal, and New York Times; and web publications like the Christian Science…
The primary goal of U.S. foreign policy during the Cold War was to deter the Soviet Union from direct aggression of any kind towards other nations, especially the West. Another important goal was to counter Communist takeovers of third-world (or other) nations through support of West-friendly governments, such as in Korea and in Vietnam.